EP1552136A1

EP1552136A1 - Fuel injection device for an internal combustion engine

Info

Publication number: EP1552136A1
Application number: EP03740027A
Authority: EP
Inventors: Friedrich Boecking
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-10-09
Filing date: 2003-05-23
Publication date: 2005-07-13
Anticipated expiration: 2023-05-23
Also published as: US7267096B2; DE10246973A1; US20060144964A1; CN1688805A; EP1552136B1; WO2004033891A1; DE50304778D1

Abstract

The invention relates to a fuel injection device (22) for an internal combustion engine, comprising a housing (30, 32). Said housing comprises a cavity (34) containing two valve elements (36, 40) which are arranged in a coaxial manner in relation to each other. Said elements cooperate with a corresponding valve seat (38, 42). The valve elements (36, 40) are associated with corresponding fuel outlets (52, 54). The aim of the invention is to produce said fuel injection device (22) with a compact structure. As a result, a common valve device (56) is provided, comprising at least three switch positions in order to influence the position of the valve elements (36, 40).

Description

Fuel injection device for an internal combustion engine

State of the art

The invention relates to a fuel injection device for an internal combustion engine, with a housing, with a recess in the housing, with at least two coaxially arranged in the recess

Valve elements which each cooperate with a corresponding valve seat and which are each assigned at least one corresponding fuel outlet opening.

Such a fuel injection device is known from DE 40 23 223 AI. In this a fuel injector for internal combustion engines is shown. Two valve needles are arranged coaxially to one another. Both valve needles each have a pressure surface. The pressure surfaces of the valve needles each delimit a pressure chamber, which is connected to a flow channel through which the fuel pressure chamber can flow. The printing areas are aligned so that with a When pressurized, lift the valve needles from the seat assigned to them, thereby releasing the corresponding openings at the end of the injection nozzle. The valve needles can be controlled independently of each other via the two independent flow channels.

The object of the present invention is to develop a fuel injection device for an internal combustion engine of the type mentioned at the outset in such a way that it is as simple and compact as possible.

This object is achieved in a fuel excitation device of the type mentioned in the introduction in that a common valve device is present which has at least three switching positions and influences the position of the valve elements.

Advantages of the invention

The fuel injection device according to the invention only requires one common valve device for operation, with which all valve elements can be controlled at least indirectly. It is therefore comparatively compact. Furthermore, since a comparatively small number of parts is required, their manufacture is also inexpensive. The fact that the common valve device provided in accordance with the invention has three switch positions enables a high degree of flexibility in the operation of the fuel injection device according to the invention.

Advantageous developments of the invention are specified in subclaims. In a first further development of the fuel injection device according to the invention, it is proposed that in a first switching position of the common valve device both valve elements rest on the valve seat, in a second switching position one of the two valve elements is lifted off its valve seat, and in a third switching position both valve elements are off their valve seats are lifted off.

In this case, the common valve device covers all essential switching states of a fuel injection device with two valve elements. The fuel injection device is therefore compact on the one hand and on the other hand enables the internal combustion engine to be operated with optimal emissions and consumption.

It is particularly preferred if the common valve device comprises a 3/3-way valve which is connected to a low pressure connection, a control chamber of the first valve element, and a control chamber of a hydraulically switchable valve device, which in turn is connected to a control chamber of a valve element and to a high pressure connection is. By using a hydraulically switchable valve device, the switching position of which is influenced by the common valve device, high fuel pressures can be achieved without the common valve device being particularly complex and / or expensive. At the same time, small leaks are nevertheless realized within the fuel injection device.

It is also proposed that in the flow path between the high pressure connection and the control chamber the hydraulic switchable valve device a flow restrictor is arranged. In this way, the closing characteristic of the hydraulically switchable valve device, and thus ultimately the closing characteristic of the second valve element, can be influenced.

Analogously to this, it is also proposed that a flow restrictor is arranged in the flow path between the control chamber of the hydraulically switchable valve device and the common valve device. The off characteristics of the hydraulically switchable valve device and thus also the opening characteristics of the second valve element are influenced by these. Above all, this enables the combustion noise of the internal combustion engine to be optimized.

It is also optimal if one valve element is pressure-controlled and the other valve element is stroke-controlled. In this case, the respective advantages of pressure-controlled or stroke-controlled valve elements can be combined in a single fuel injection device. For example, a pressure-controlled valve element has a particularly favorable injection characteristic, in particular in part-load operation of the internal combustion engine.

The control of the pressure-controlled valve element is simplified in that the pressure-controlled valve element is arranged radially outside of the stroke-controlled valve element.

In a further development, it is again advantageous if the control chamber of the pressure-controlled valve element is connected to the hydraulically switchable valve device. The advantages of the hydraulically switchable valve device with regard to low leakage and high pressure are particularly significant in connection with the control of a pressure-controlled valve element.

In a further embodiment of the fuel injection device, it is also proposed that in an end position of the common valve device, the control chamber of the stroke-controlled valve element and the control chamber of the hydraulically switchable valve device are only connected to the high-pressure connection. In this switching position of the common valve device, both valve elements are in their closed position, that is to say in contact with the respective valve seat.

drawing

A particularly preferred exemplary embodiment of the present invention is explained in detail below with reference to the accompanying drawing. The drawing shows:

Figure 1 is a schematic representation of a

Fuel system of an internal combustion engine with a plurality of fuel injection devices;

Figure 2 is a partial section through one of the

Fuel injectors of Figure 1; and

FIG. 3 shows an enlarged illustration of a region of the fuel injection device from FIG. 2.

Description of the embodiment In FIG. 1, a power-fueling system bears the reference number 10 overall. It comprises a fuel tank 12, from which an electric fuel pump 14 requests the fuel m from a low-pressure fuel line 16. The

Low-pressure fuel supply 16 leads to a high-pressure fuel pump 18. This is a piston pump which is driven by a camshaft (not shown) of the internal combustion engine to which the fuel system 10 belongs. The

High-pressure fuel pump 18 prompts in a fuel rail 20, in which the fuel is stored under high pressure.

A plurality of injectors 22 are connected to the fuel collecting line 20 and inject the fuel directly into the combustion chambers 24 of the internal combustion engine that are assigned to them. The operation of the internal combustion engine and the fuel system 10 is controlled and regulated by a control and regulating device 26. In particular, the injectors 22 are also controlled by the control and regulating device 26. A line 28 leads from the injectors 22 back to the fuel tank 12.

A region of one of the injectors 22 is shown in detail in FIG. 2:

The injector 22 comprises a two-part housing with an upper part 30 and a lower part 32. In the housing 30, 32 there is a recess 34 in which, among other things, a first elongated valve element 36 is present. Its lower end in FIG. 2 is tapered to a point and works with a valve seat 38 (see FIG. 3) in the lower part 32 of the housing. Coaxial to the first Valve element 36 and radially outside of this there is a second valve element 40, the likewise conical tip of which cooperates with a valve seat 42 in the lower part 32 of the housing.

The first valve element 36 is acted upon by a compression spring 44, one end of which is supported on a shoulder (without reference number) in the upper part 30 of the housing, in the direction of the valve seat 38. Analogously to this, the second valve element 40 is acted upon by a compression spring 46 in the direction of the corresponding valve seat 42. The compression spring 46 is not supported directly on a shoulder in the recess 34 in the upper part 30 of the housing, but on an intermediate ring 48.

The recess 34 in the lower part 32 of the housing comprises a blind hole 50, from which a plurality of outlet openings 52 lead to the outside. Through these outlet openings 52, the fuel, as will be explained in greater detail below, occurs when the first is open

Valve element 36 and open second valve element 40. Outlet openings 54 serve analogously to the outlet of the fuel when only the second valve element 40 is lifted off the second valve seat 42. This will also be explained in more detail below.

For the actuation of the two valve elements 36 and 40, a common valve device 56 is provided, which is arranged in the upper region of the upper part 34 of the housing. This comprises a semi-spherically shaped valve element 58, which is arranged in a switching chamber 60. Via a tappet 62, the valve element 60 can be moved from a piezo actuator 64 shown only symbolically different switch positions can be adjusted.

In the rest position, the valve element 58 is pressed against a valve seat 68 by a compression spring 66. If the valve element 58 abuts the valve seat 68, the

Connection from the switching chamber 60 via a channel 70 to a low-pressure connection 72 (see also FIG. 1) is interrupted. The low-pressure connection 72 is in turn connected to the return line 28 / which leads back to the fuel tank 12.

A channel 74 leads from the lower end wall of the switching chamber 60 in FIG. 2 to a control chamber 76. The upper end of the first valve element 36 with a pressure surface 78 in FIG. 2 also opens into the control chamber 76. A flow restrictor 80 is present in the channel 74. From the radial boundary wall (without reference number) of the switching chamber 60, a fluid connection (without reference number) leads via a flow restrictor 82 to a control chamber 84 of a hydraulically actuated switching valve 86.

The hydraulically actuated switching valve 86 likewise comprises a switching chamber 88 in which a valve element 90 is arranged. The valve element 90 is generally cylindrical with a switching section 92, which has a circular cylindrical diameter, a transition section 94, which is designed like a constriction, and a circular cylindrical guide section 96. One end of a compression spring 98 is supported on a closure part 100. The other end of the compression spring 98 acts on the valve element 90 in the direction of the control chamber 84. An annular groove 102 is provided in the peripheral wall of the switching chamber 88. On the one hand, this is connected via a channel 104 to a high-pressure connection 106 (cf. also FIG. 1). This in turn leads to the fuel collecting line 20. On the other hand, a channel 108 leads via a flow restrictor 110 from the annular groove 102 to the control chamber 76, with which the movement of the first valve element 36 is controlled. From that section of the peripheral wall of the switching chamber 88, which lies approximately in the region of the constricted transition section 94 of the valve element 90, a channel 112 leads to an annular space 114 in the lower region of the second valve element 40.

In FIG. 2 to the right of the annular groove 102, the peripheral wall of the switching chamber 88 forms a valve seat 116 for a switching edge 118 of the valve element 90. The switching edge 118 is formed between the switching section 92 and the transition section 94. In the switching section 92 of the valve element 90, a further channel 120 extends obliquely to the longitudinal axis of the valve element 90. This comprises a flow restrictor 122 and connects the annular groove 102 to the control chamber 84. A leakage channel 124 should also be mentioned, which extends from the recess 34 in Upper part 30 of the housing leads to a leakage connection 126.

The injector 22 shown in FIGS. 1 to 3 works as follows:

In the first rest position, the valve element 38 of the common valve device 56 rests on the upper valve seat 68 in FIG. In the switching chamber 60 of the common valve device 56, in the control chamber 76 of the first valve element 36, and in the control chamber 84 of the hydraulically actuated switching valve 86 is therefore on High pressure connection 106 present high pressure. As a result, the valve element 92 of the hydraulically actuated switching valve 86 is printed with the switching edge 118 against the valve seat 116. That area of the switching chamber 88 which is at the level of the transition section 94 is therefore separated from the high-pressure connection 106. Therefore, it has a comparatively low pressure. The same applies to the channel 112 and the annular space 114. The second valve element 40 can therefore be pressed against the valve seat 42 by the spring 46.

Because there is a high fuel pressure in the control chamber 76 and thus also on the pressure surface 78, but at the same time there is a low pressure (combustion chamber pressure) in the blind hole 50, the valve element 36 is also pressed against the valve seat 38. In this first switching position of the common valve device 56, in which the valve element 58 rests on the valve seat 68, the injector 22 is thus closed and no fuel escapes from the openings 52 and 54.

The valve element 58 of the common valve device 56 can be brought by the actuator 64 via the tappet 62 into a second switching position, in which it rests on the lower boundary wall of the switching chamber 60 in FIG. 2. The switching chamber 60 is now connected to the low pressure connection 72 via the channel 70. The high pressure can thus escape from the control chamber 84 of the hydraulically advisable switching valve 86 via the flow restrictor 82. By the compression spring 98 is now

Valve element 90 of the hydraulically actuated switching valve 86 is moved in the direction of the control chamber 84, so that the switching edge 118 lifts off the valve seat 116. The fuel present in the annular groove 102 under high pressure can now flow into the annular space 114 via the channel 112. The high one is now located on a region radially outside the valve seat 42 of the lower conical end face of the valve element 40 in FIG

Fuel pressure that is also present at the high pressure connection 106. This moves the second valve element 40 upward against the action of the compression spring 46, so that it comes free from the valve seat 42. The fuel present under high pressure in the annular space 114 can thus flow outward through the outlet openings 54.

Since the Ventilele ent 58 of the common valve device 56 in this second switching position, the channel 74

Closes control chamber 76, there is still a high fuel pressure in it, which presses the first valve element 36 downward over the pressure surface 78 in FIG. Although a high fuel pressure is now applied to the region of the conical lower end surface of the valve element 36 located radially outside of the valve seat 38, the first valve element 36 is pressed further against the valve seat 38 due to the resultant downward force of the pressure surface 78 in FIG. No fuel can therefore continue to escape through the outlet openings 52.

So that the pressure in the control chamber 76 does not drop so much that the valve element lifts off the valve seat 38 even during the movement of the valve element 58 of the common valve device 56 from the first to the second switching position, the flow throttle 80 causes the fuel to flow out of the control chamber 76 delayed.

The valve element 58 of the common valve device 56 can also be brought into a third, middle switching position by the actuator 64. In this it is neither on the valve seat 68 nor on the lower end wall of the switching chamber 60 in FIG. 2. Thus, as in the second switching position, the switching chamber 60 with the

Low pressure connection 72 connected. In addition, however, the fuel can now flow out of the control chamber 76 via the channel 74 and the flow restrictor 80 into the switching chamber 60 and further to the low-pressure connection 72. As a result, the pressure in the control chamber 76 drops so far that the

Ventilele ent 36 is lifted from the valve seat 38 by the high pressure applied to the conical end face on the radially outside of the valve seat 38. If the valve element 58 of the common valve device 56 is thus in the middle third switching position, the

Injector 22 dispenses fuel both through the outlet openings 54 and through the outlet openings 52.

Claims

Expectations

1. Fuel injection device (22) for an internal combustion engine, with a housing (30, 32), with a recess (34) provided in the housing (30, 32), with at least two valve elements arranged coaxially in the recess (34) (36, 40), which each work with a corresponding valve seat (38, 42) and which each have at least one corresponding one

Fuel outlet opening (52, 54) is assigned, characterized in that there is a common valve device (56) which has at least three switching positions and influences the position of the valve elements (36, 40).

2. Fuel injection device (22), characterized in that in a first switching position of the common valve device (56) both valve elements

(36, 40) rest on the valve seat (52, 54), in a second switching position one of the two valve elements (40) is lifted off its valve seat (54), and in a third switching position both valve elements (36, 40) off their valve seats ( 52, 54) are lifted off.

3. Fuel injection device (22) according to one of claims 1 or 2, characterized in that the common valve device comprises a 3/3-way valve (56), which with a low pressure connection (72), a control chamber (76) of the first valve element (40), and a control chamber (84) of a hydraulically switchable valve device (86), which in turn is connected to a control chamber (114) of a valve element and to a high-pressure connection (106).

4. Fuel injection device (22) according to claim 3, characterized in that a flow restrictor (122) is arranged in the flow path between the high pressure connection (106) and the control chamber (84) of the hydraulically switchable valve device (86).

5. Fuel injection device (22) according to one of claims 3 or 4, characterized in that a flow restrictor (82) is arranged in the flow path between the control chamber (84) of the hydraulically switchable valve device (86) and the common valve device (56).

6. Fuel injection device (22) according to one of the preceding claims, characterized in that the one Ventilele ent (40) pressure-controlled and the other valve element (36) works stroke-controlled.

7. Fuel injection device (22) according to claim 6, characterized in that the pressure-controlled valve element (40) is arranged radially outside of the stroke-controlled valve element (36).

8. Fuel injection device (22) according to one of the preceding claims, characterized in that the control chamber (114) of the pressure-controlled valve element (40) is connected to the hydraulically switchable valve device (86).

9. Fuel injection device (22) according to claim 8, characterized in that in an end position of the common valve device (56) the control chamber (76) of the stroke-controlled valve element (36) and the control chamber (84) of the hydraulically switchable valve device (86) only are connected to the high pressure connection (106).